Metal spray gun



Dec. 30, v1941. r w. M.l BRITTON Y 2,268,202

METAL SPRAY GUN 4 Sheets-Sheet l Filed Nov. 22, 1935 WMI MM? ATTORNEY Dec. 30, 1941. w. M. BRlTroN 2,258,202

METAL SPRAY GUN4 2 Filed Nov. 22, 1935 4 sheets-sheet 2 A TTORNEYS.

Dec. 30, 1941.

Filed Nov. 22, 1935 w. M. BRITTON METAL SPRAY GUN 4 Sheets-Sheet 5 I j @im INVENTOA Millian? f7. Brfal? ATTORNEYS.

'Dec'. 3o, 1941.

W. M. BRITTON METAL SPRAY GUN Filed NOV. 22, 14935 4 Sheets-Sheet 4 INVENTOR.

A TTORNEYS,

Patented Dec. 30, 1941 UNITED STATES PATENT OFFICE 2,289,202 METAL SPRAY GUN William M. Britton, Detroit, Mich. Application November 22, 1935, Serial No. 50,997

9Claims.

This invention is an apparatus for spraying molten metal commonly known as a metal spray gun, and is used for applying and intimately bonding a layer of metal to the surface of any the coating of a part made o'f a tough or of a soft cheap metal `with `a hard wear-resisting metal, or in the coating of a strong metal with a bearing metal, or in the applying of coatings of alloys, such as leaded bronze, by spraying a wire made up of a lead or lead-tin inner wire with a copper strip folded around the` inner wire. This method of alloying gives a thoroughly uniform mixture of the metals, which result is difficult to obtain in any other way. It is also useful in coating non-metallic surfaces with metal, as in put` ting a metal finish on stone, concrete, plaster, or other surfacesr as is sometimes required in modern decoration, or in putting 'a metal finish on non-metallic decorative objects such as statues. '-Metal spray guus prior tothe gun of the present inventiongenerally have beendriven by air turbines which stall easily by `kinks in the wire to be melted and sprayedby the gun. In contradistinction to conventional practice, the gun of the present invention utilizes a positive displacement air motor to drive the feeding mechanism `and thus provides a "gun which does` not easily jam due to irregularities in the feed wire. l

In metal spray guns made prior to the present invention it is necessary to insert a wire in the' `wire passage of the gas nozzle before lighting the oxyacetylene gas, ineorder to prevent the gas which the metal wire or rod is fed by means of a positive displacement air motor whose torque will increase as the motor is slowed down by external resistance, the torque rising toits maximum as the speed of the motor approaches zero, so that the material-feeding means will be abletc overcome such irregularities as kinks in the wire.

Another object of the present invention is to provide a metal spray gun having a positive displacement air motor which actuates a wire-feeding mechanism which will permit the gun to spray eilfectively. at the proper rate of wire feed, all of the different kinds of metal withoutchanging gears or making changes in the wire-feeding mechanism.

Another object of the present invention is to provide a self-adjusting mechanism for feeding the wire or rod to be melted and sprayed which automatically accommodates selected different sizes of materials fed therethrough so that variations in the size of the wire or rod being fed to` the gun will not affect its operation and so that the size of material being fed can be changedA pressure in the wire-melting chamber from forcingV the flame back through the wire passage of the gas nozzle and thereby overheating and burning other parts of the metal spray gun. In the present invention the flame in the wire-melting chamber is prevented from owingback through the wire passage in the gas nozzle, and thus prevents the flame,` in the wire-melting chamber from overheating the empty` gun.v

the feeding mchanism.` More specifically, an embodiment ofthe present invention providesa spray gun which cantake in, melt, and spray any wire or rod from nl, of an inch to 1% of an inch in diameter, or even larger if desired, without it being necessary to `change or adjust any parts of the gun except the flame nozzle and the gas nozzle, the wire-feeding mechanism being suillciently' flexible to accommodate without manual adjustment the varying sizes of wire or rod l within selected limits forwhich the gun is designed.

Another object of the present invention is to provide a metal spray gun in which the feeding means can adjust itself to variations in the size of the wire or rod beingfed while feeding the wire or rod forward on a predetermined straight path and without deviating therefrom.

Another object of` my invention is to provide a metal spray gun in which the feeding `means grips the wire or rod being fed with a force which is directly proportional to the resistanceto feeding and whichautomatically increases as the re sistance to feeding increases.

Another object of the present invention is to provide a metal spray gun in which the air motor isf properly lubricated by a novel arrangementfor automatically and continuously supplying a predetermined amount of oil` thereto.

Another object of the present invention is to provide a.v metal spray gun .iri which separate compartments are provided for separate kinds of lubricants adapted to particular purposes; for

example, a fast turning `worm on the motor shaft and its accompanying worm wheel can be supplied with light oil while slower turning gears can be packed with the proper kind of heavier grease.

Another object of the present invention is to provide a metal spray gun in which the hollow handle serves as a mufiler and as a passage for the air exhausted from the motor, the interior of the handle being arranged with sound absorbing material or baffles if desired.

Another object of the present invention is to provide a metal spray gun in which the feeding of metal isrunder the instant control of the operator, the gun being provided with a trigger in front of the handle which stops the Vfeeding when itis pulled back by forcing the drive wheels apart.

vThis trigger control of the drive wheels also permits the wire to be readily inserted in the gun or withdrawn.`

Another objectof the present invention is to provide separate valves for controlling the air which operates the motor and the air which atomizes the molten metal so that the rate of feed can be easily regulated and the degree of atomization can also be regulated, independently of each other. f This feature of the invention is particularly valuable in the spraying of metals which have a low melting point, and when it is desired to deposit the molten metal as hot as possible so that the metal being sprayed will fuse with the metal already deposited. The spraying of metal of low melting point requires the highest rate of feed of the metal wire being sprayed, which in turn requires a high air pressure for theair motor. In order to deposit the kmolten metal so that it will fuse with the metal already deposited it is necessary to use a lower pressure and volume of the atomizing air. 'Ihis result is accomplished in the present invention by the use of the separate air control valves for the air motor and for the atomizing air.

Another object of the invention is to provide a metal spray gun in which there are positive means to hold the motor throttle -in adjusted position so that the'vibration, if any, of the motor and other mechanism will not change the adjustment of the valve controlling the air passing to the air motor.

Another object of the present invention is to provide a metal spray gun which is designed to provide xed atomizing air jets which do not require adjustment and which are so placed as to discharge into the bore of the llame nozzle and so close to the molten metal that atomization of the metal is positively and quickly acv complished by the air passing through such jets.

Another object of the present invention is to provide a mixing valve in the nature of a stop cock for a metal spray gun which permits the fuel, oxygen-and compressed air required by the gun to be turned on or off by a single control lever, and inV which provision is made to prevent leakage of the compressed air into the passages carrying fuel and oxygen at a lower pressure.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification, in which is shown one preferred embodiment of the invention and wherein like reference characters designate corresponding parts in the several views.

Fig. 1 is a side elevation of a spray gun of the present invention, with a part of the handle and base broken away to show the exhaust passage from the air motor.

Fig. 2 is a front elevation of the spray gun of the present invention.

Fig. 3 is a plan view of the gun shown in Figs. 1 and 2, with part of the flame nozzle andspray head broken away to show the air and gas passages therein, and to show more clearly the structure of the gas nozzle.

Fig. 4 is a rear elevation with the rear gear case cover plate removed to show the arrangement of the gearing. l

Fig. 5 is a section taken substantially on the line 5 5 of Fig. 3 in the direction of the arrows.

Fig. 6 is a section taken substantially on the line 6-6 of Figs. 5 and 7 in the direction of the arrows.

Fig. '7 .is a section takensubstantially on the lines 1-'1 of Figs. 1, 5, 6 and 8, in the direction of the arrows.

Fig. 8 is a section taken substantially on the lines 8 8 of Figs. '7 and 14 -in the direction of the arrows, but with the rotor and blades of the motor shown in elevation.

Fig. 9 is a plan view of the back part of the gun with the top gear case cover and the parts above it removed to show the parts inside of the upper compartment of the gear case.

Fig. 10 is a section taken substantially on the lines I0--I0 of Figs. 5 and 11 in the direction of the arrows.

Fig. 1l is a central vertical section taken substantially on the line H-II of Fig. 3 in the direction of the arrows.

Fig. 12 is a section taken substantially on the lines |2--I2 of Figs. 1, 3 and 11 in the direction of the arrows.V

Fig. 13 is a diagrammatic sectional View taken substantially on the lines |3a,` |3b and I3c of Fig. 12 showing the relative positions of the ports in the stop cock and the relations to the gas, oxygen and air ducts in the spray head when the stop cock is in the position to supply only acetylene to the gas nozzle at a time prior to ignition and formation of the melting ilame.

Fig. 14 is a section taken substantially on vthe line |4--I4 of Fig. 12 in the direction of the arrows.

Fig. 15 is a section taken substantially on the line l5-I5 of Fig. 5 in the direction of the arrows.

Fig. 16 is a section taken substantially on the line |6|6 of Fig. 12 in the direction `of the arrows. 1

Before explaining in detail the present invention it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation, and it is not intended to limit the invention claimed herein beyond the requirements of the prior art.

The preferred form of the gun illustrated by way of example in the accompanying drawings (see Fig. 3) has three main parts, a spray head I, a motor case 2, and a gear case 3, which are secured together by means of studs 4 which are screwed into the front of the gear case 3 and extend through the motor case and spray head.

Nuts on the ends of the studs hold these three main parts tightly together. The spray head I. the motor case 2, and the gear case 3 are mounted 'on top of a one-piece base 6 and handle 1 by means of a screw 8 (Fig. 11) which extends up through a lug 9 at the front of the baseinto the bottom of the spray head I, and a pair of screws III at the back of the base (Fig. 1), one on each side of the handle, extending up into the gear case 3.

Three nipples II, I2 and I3 for acetylene, oxygen and air respectively, are screwed into three holes I4, I5 and I6 respectively in the bottom ofthe spray head at the front of the gun. The acetylene and air nipples are side by side and the oxygen nipple lies between and in front of them.

A main stop cock I1 (see Figs. 11 and 12) lies in a conical seat or bore I8 in the lower part of the spray head I and is directly above the acetyleneand air nipples II and I3. A short drilled acetylene duct I9 leads up fromthe hole I4 into which the acetylene nipple II is screwed and serves to conduct acetylene from the nipple to the stop cock. A main air duct 23 extends vertically up from the hole I6, into which the air nipple I3 is screwed, through the seat I8 of the main stop cock, and upto the top of the spray head I. A drilled passage 2|, 22 extends up from the bottom of the spray head I to the` top, passing through the seat I8 of the main Y stop cock. The upper part of this passage forms the gas duct 2I, while the lower part forms the oxygen duct 22 whose lower end is plugged by a screw 23. A horizontally drilledA hole forms a connecting duct 24 between the `hole I5 into which the oxygen nipple is screwed and the oxygen duct 22, the forward end of the drilled passage being plugged by a screw 25.

The stop cock IIhas an acetylene hole 25 and an oxygen hole 21 which are placed so as to register with the acetylene and oxygen ducts I9 and 22 respectively as the stop cock is turned. Thesetw holes 26 and 21 lead to a gas mixing chamber 28 which is bored in from the end of ""N'the stop cock I1. On the other side of the stop cock and opposite the acetylene and oxygen holes is a gas hole 29 which is located so as to register with the lower end of the gas duct 2I. An air hole 38 extends directly throughthe stop cock II and is placed so as to be aligned with the main air duct 20.

As shown in Figs. 11, 12 and 13, the various holes 24, 21, 29 and 3l! in the main stop cock are of different sizes and are not parallel, the gas hole 29 in particular being larger than the oxygen hole 21. They are so arranged that as the stop cock is rotated from its closed position with the handle 4I extending straight forward, towards its open position with the handle extending straight down, the acetylene hole and the gas hole begin to come into registry with their respective ducts rst. This allows acetylene to reach and iiow `out of the nozzle before oxygen is supplied thereto and before air is supplied to either the motor or the nozzle, so that bore 34 in the side of the spray head I and concentric with the stop cock I1. The spring is held which is secured tothe stem 32 `of the stock cock by a tapered pin 42 to allow the stop cock to be turned through only 90;

If the stop cock I'I is not a perfect fit in its bore I8, a slight leakage will voccur along the 'bore from the air hole I6 to the oxygen hole I4,

unless means are provided to prevent it. Such leakage occurs because the air is at a much higher pressure than the oxygen and the acetylene and results in dilution of the oxygen and acetylene so that the ame will not burnproperly when the gases are first turned on, and, if allowed to continue so that the pressure builds up in the gas holes, may cause damage. Such leakage can be prevented by careful periodical lapping of the valve, but these operations are costly and unsatisfactory in a commercial gun. To eliminate such lapping, I provideftwo small grooves, one 43 extending around the stop cock I1 between the air hole30 and the oxygen and gas holes 21, 29, and the other 44` extending around the inside of the bore I8 and being so placed as to form with the groove 43 an annular duct lying half in the stop cock and` half in the wall of the bore. This annular duct Vis vented toward the front of the spray head by a vent 45 so that any air which leaks along the stop cock is vented to the exterior of the gun.

The upper part of the spray head I (see Figs. 3 and 11) carries on its front face the atomizing air chamber 5I which is formedby a forwardly projecting annular wall 52 and a ame nozzle 53. The nozzle is secured to the front of the atomizing air chamber by means of a cylindrical cap 54 which fits over it and screws on to the exteriorly threaded wall 52 of the atomizing air chamber. Extending rearwardly through the spray head I from the atomizing air chamber is a cylindrical gas chamber 55 into which the gas duct 2| opens. A gas nozzle 55, preferably of stainless steel, extends through the gas chamber 55, and the rear end of the head 51 of the nozzle 58 fits into the front end of the gas chamber 55. The head 51 of the gas nozzle 55 has a circumferential flange 58 which lies against the back of the atomizing air chamber 5I and which holds `the head of the nozzle from sliding into the gas chamber 55. A collar 59 surrounds the stem of the gas nozzle and nts into the rear part of the gas chamber 55.

length of the gas nozzle, including an extension il which extends out in back of the nut 64, is

plerced by a bore 86 through which the wire 50 is fed into the flame nozzle 58.

' The head 51 of the gas nozzle (see Fig. 11) `is pierced by six smalljet holes 81 which extend forward from the gas chamber 55 to the front of `the nozzle and converge towards the end of the wire 50. The gas in the gas chamber 55, a mixture of acetylene and oxygen, flows out of these jet holes and forms upon ignition an oxyacetylene flame which converges upon and melts of the gas nozzle projects forward into the bore 58 of the il'ame'nozzle and has an annular series of lands-,10 (see Fig. 3) on its rim, the topsof the lands tting against the surface of the bore 88. The grooves 1| between the lands form air passages opening from the atomizing air chamber 5| `into the bore of the flame nozzle and serve to direct a thin annular sheet of air along vthe surface of the borel to protect the flame nozzle from the heat' of the flame which is melting the wire 50. The flame nozzle (see Fig. 11) is pierced by six sharply converging air jet holes 12 leading from the atomizing air chamber 5I to the bore of the nozzle. The atomizing air jets issue from these holes and impinge upon the molten end of the wire 50 and atomize it and spray it on the work to be coated. The atomizing air reaches the atomizing air chamber (see Fig. 3) through a duct 18 leading from the upper end of the main air duct 20. The atomizing air is controlled by a cock 14 (see Fig. 12) which screws into the side of the spray head and intercepts' the duct 20. Theend of the cock 14 has a hole 15 lthrough which the atomizing air can flow whenV the hole is aligned with the air duct 20. A lock `-nut 16, threaded onto the atomizing air control cock 14 and screwing up against the side of the spray head I, serves to hold the cock in its adjusted position.

A drilled passage 11 (see Figs." 3, 11 and 12) leads diagonally back to the rear face of the spray head from a point 18 in the air duct 20 `lust below the atomlzing air control cock 1-4.

This passageconnects with a series of passages 19, 80, 8| and 82, which terminate in a jethole 88 and form a duct to lead compressed air thereto. This jet hole 83 lies in back of and below the vend of the bore 68 in the flame nozzle 56 and is aimed so as to direct a jet of air into the bore of the llame nozzle when the wire 50 is withdrawn. This jet of air entering the rear end of the gasr nozzle prevents the flame in the bore of the flame nozzle from flowing back through the gas nozzle when the` gun has been lit and before a wire is inserted or when the gun has used up a piece of wire and a new piece has not yet been fed into place. When a wire is in place, the jet strikes the bottom of the wire and is deilected to the sides so that it does not ilow through the wire passage in the nozzle and lower the temperature of the oxyacetylene flame.

The flame nozzle is kept from overheating by the atomizing air jets which flow through it and cool it and by the jets of air fromthe grooves 1I which shield it from the heat of the flame.` The gas nozzle is kept from overheating by the gas ilowing through the jet holes 61 and by the air flowing through the grooves 1I between the lands 10 on its rim (see Figs. .3 and l1).

The spray head I (see Fig. 14) carries the means for controlling the supply of air to the motor. This consists of a throttle sleeve 84 pressed into a transverse horizontal hole just in back of the main air duct 20. The throttle 85v screws into the threaded bore of the sleeve 84 and has a conical end 86 which fits into the hole 81 in the end of the sleeve, forming a needle valve.

Air reaches the interior of the sleeve around thek base ofthe conical end 86 of the throttle through a connecting duct 88 which is drilled from the back of the spray head after thesleeve 84 has been pressed into place and before the throttle 85 is screwed in, the end of the duct near the motor case 2 being plugged by a screw 8B. The hole 81 in the throttle sleeve connects to a motor` air duct 90 which serves to lead the air from `the throttle to the motor case.

'I'he shell of the motor (see Figs. 7 and 8) is composed of a cylindrical. motor liner |00 and circular front and rear end plates I0|, |02. These three circular parts are prevented from rotating by a key |03 which lies partly in a groove in the motor case and partly in a groove in the motor liner and in notches in the edges of the motor end plates IOI, |02. The shaft |04 of the motor extends horizontally through the motor liner and end plates and is eccentric thereto. 'I'he front end of the shaft is carried by the inner race |05 of a ball bearing whose outer race |05 is slidably mounted in a cylindrical recess |01 in the back face of the spray head I. The rear part of the shaft |04 passes through and is supported by the inner race |08 of a second ball bearing at the back of the motor. The outer race |09 of this second bearing is slidably supported `in a cylindrical recess |I0 which is coaxial with the vrecess |01 in the spray head and is formed in a boss III which projects rearwardly from the main body of the motor case 2 into the gear case 3. The rotor A|I2 of the motor is pressed onto the shaft and lies between the two inner bearing races |05 and |08, being separated therefrom by sleeves |I3 and |I4. A spring rwasher |I5 rests in the back of the recess ||0 at the back of the motor case and presses the outer race |08 of the rear ball bearing forward. The outer race |08 of the front' bearing is held back by anv acUusting plate IIS which lies in front of the front bearing in the recess |01 and which has a rim which bears against the outer race. This adjusting plate is positioned by means of an adjusting screw I I1. This screw screws in from the front of the spray head I and bears against the center of the adjusting plate IIB and is secured in position by a lock nut II8. The inner and outer races |05, |08, |01, |08 of both bearings are so formed that they will transmit thrust from the spring washer II5 to the adjusting plate IIS. Thus, by turning the adjusting screw ||1 in and out, the rotor I I2 can be adjusted back and forth so that it will have equal clearance at both ends.

The rotor I I2 has four slots II! spaced equally around its circumference and extending parallel to and at one side of the shaft |04. Each of these slots contains a rectangular vane |20 made of Bakelite or other suitable material which can slide in and out of the slot with its rounded outer edge bearing against the inner surface of the motor liner |00 as the rotor turns. The front end of the rotor has` four small groves I2I which lead from the shaft |04 to the bottoms of the slots H9. These grooves serve to admit air to the varies |20. The air reaches these grooves from the throttle opening 81 (see Fig. 14)` by passing successively through the `motor air duct 90, through a connecting slot |22 in the back of the spray head between the motor air duct 90 Aand `the front motor bearing recess |01, through the clearance space between the front motor bearing |05|06 and the front motor end plate |0|, and through the clearance space between the front motor shaft sleeve ||3 and the sides of the shaft hole in the front motor end plate I0|. The air thus admitted under the vanes |20 pushes them out against the` inner surface of the motor hner when the throttle is opened to supply air to the motor, preventing the air from flowing around the rotor without acting on it.

The air which turns the rotor enters the upper part of the motor case 2 from the duct 90 in the spray head through the duct |23 which registers with it. This air passes through' the inlet ports |24 in the motor liner and, being under pressure pushes against the Vanes at each side of the port.

Due to the relative position of the ports |24 and the` shaft |04, the vane which lies to that side of the port in which it is desired that the motor turn, presents a larger area to the pressure of the air than theiother. The unbalanced force, resulting from the unequal areas, turns the rotor. Similar unbalanced forces on the opposing faces of adjacent blades lying between the inlet ports |24 and the exhaust ports |25 in the direction in which the rotor turns also causerotation of the rotor. A large number of exhaust ports |25, spaced around the lower part of the motor piece of cork |28 which serves to frictionally hold an oil wick |29 in place. 'Ihe upperend |30 of i this wick projects through` the wall of the oil chamber |26 and rests on the motor liner |00 directly in line with the motor air duct. The oil chamber |26 contains a quantity of light oil, such as spindle oil, into which the lower end of the wick dips, thus keeping the wick saturated. The air entering the motor` case through the duct |23 impinges upon the end of the wick and picks up minute drops of oil which are carried into the motor and serve `to lubricate it. Inl order that the oil supply may be replenished without removing the plugi|21 and disturbing the wick, an oil chamber lling hole |32 is provided in the top of the motor casing which is closed by a plug |33 which screws lnto it.

'I'he gear case 3 (see Figs. 4, 5 and 6) is divided into three compartments by an upper horizontal partition |38 and a lower longitudinally extending L-shaped partition` |39. The space between the two partitions forms a high speed gear compartment |40. The rectangular space at one side of the lower part of the gear case enclosed by the L-shaped lower partition forms an intermediate speed gear compartment and the space in the top of the gear case whose bottom is formed by the upper partition |38 forms a lowspeed gear compartment |42.

The back of the gear case is closed by a removable rear gearcase cover |43 secured in place by screws extending into the tapped holes |44 in the body of the gear case. This rear cover has sh'aft being in the high speed gear compartment |40. This shaft is journalled in bronzebushings |49, |50 and |5| which are inserted in holes in i the sides of the motor case 3 and in the partition |39. The part of the shaft in the intermediate speed compartment |4| carries a worm |52 which is secured thereto by means of a set screw. One end of th'e worm bears against a collar on `the bushing |50 and the space between the other end` of the worm and the collar on the bushing i,

|49 is filled by a washer |53 whose thickness may be varied to secure the proper end clearance. This arrangement positions the shaft axially. The part of the shaft in the high speed gear compartment carries a worm gear |54., and the ends of the shaft lying in the bushings |49 and |5| in the sides of the gear 3 are enclosed by cover plates screwed onto the sidesvof the gear case. The worm gear |54 is driven by the worm |56 which is secured onto the rear` end of the motor sh'aft |04 which projects into the high speed gear compartment |40 of the gear ease 3 from the rear motor bearing boss `The worm gear |54 and the worm wheel |56. arevlubricated by means of a` felt pad |51, in the bot- -tom of the gear case. This pad is kept saturated with thin oil, such as spindle oil, and bears lightly against one side of the worm gear |54. The n this shaft is journalled `in a bushing |6| pressed into a hole in the` bottom of the gear case 3 and the central portion is journalled in a bushing |62 pressed into the part of the partition |39 forming the top of the intermediate `speed gear compartment I4 I.

The drive gear shaft |59 lies in the rear portion of` and to the left of the center of the gear case 3. A similar drive gear shaft |63 is disposed symmetrically with respect to the drive gear shaft |59, the lower end of the shaft being journalled in a bushing |64 similar to the bushing |6|. This shaft, however, lies wholly in the high speed gear compartment |40 and in the low speed compartment |42, and does not carry a worm wheel.

Two yoke arms |65, |66 (see Figs. 5 and 10') are located in the upper low speedgear compartment |42 and are carried by` depending sleeves |61, |68 which are journalled in bearing bosses |69. Thesebosses project downwardly from the upper gear case partition |38 into the large high speed `gear compartment |40. The holes in the bearing bosses |69 are lined by bronze bushings |10 which form bearings for the'yoke arm sleeves |61, |68 and bearing washers |1| around the yoke arm sleeves space them from the partition |38. The bosses |69 and the yoke arm sleeves I 61, |68 are coaxial with the bushings |12 which form bearings which support the upper ends of the drive gear shafts |59 and |63. The ends of the yoke arms |65, |66

`which are secured to the sleeves |61, |68 are provided with engaging gear teeth |13, |14 which make the two arms move the same amount when they swing in or out. a

A pair of drive gears |15, |16 (see Figs. 5 and 9) are securely pressed onto the enlarged upper ends |11 of the drive gear shafts |59, |63 above the yoke arms |85, |66, being spaced therefrom by means of bronze bearing washers |18. These gears mesh so that the right drive gear |16 is driven from the left drive gear |15, which in turn is driven through the left gear shaft |59 by the worm gear |58. The forward ends of the yoke arms carry upwardly extending vertical drive wheel supporting pins |19 which are pressed into holes in the yokes. 'I'hese pins (see Fig. 5) project through transverse oval apertures |80 in the top gear case cover |46. These apertures are large enough to also accommodate the upwardly projecting hubs |8| of a pair of drive wheel pinions |82, |83 which are journalled on the two drive wheel supporting pins |19. Washers |85 serve to close the part of the aperture not occupied by the drive wheel supporting pins |19 and the hubs |8| of the drive wheel pinions |82, |83.

The' topsv of the hubs |8| are each formed into three upwardly projecting clutch teeth |86 which engage. similar downwardly projecting clutch teeth |81 which are formed on the bottoms of the hubs |89 of a pair of drive wheels |90. The rims of the`drivefwheels are concave and are serrated so as to centerthe wire placed between them and secure a driving engagement with it. These drive wheels are journalled on the drive wheel supporting pins |19 and are supported bybronze washers |9| which rest upon the upper surface of the top gear case cover rplate |46. They are held in place by means of retaining collars |92 secured to the tops ofk the drive wheel supporting pins |19 by means of cotter pins |93. The col- .lars are provided with circumferential grooves |94 into which the heads and the spread ends of the cotter pins flt.

The front ends of the yoke arms have inwardly directed projections |95 (see Figs. 10 and l5) which almost meet the central vertical plane of the gun. The bottom edges |96 of these projections |95 are beveled and rest against a conical head |91 on a vertically extending yoke control I apart. This separates the drive wheels |90 and rod |98. The head normally rests in a recess |99 in the partition |38 forming the bottom of the upper gear compartment |42. The yoke control rod (see Fig. 5) extends down through the gear case 3 and projects out from the bottom thereof through a bushing 200 into a hollow boss 204 within the base 6 (see Fig. 8). The lower end 202 of the yoke control rod |98 lies in a vertical slot 203 in a central boss 204 on top of the Vfloor of the hollow base 6.

|66 carrying the drive wheels are pressed towards each other by means of U-shaped springs 2|0 (see Fig. 10) which rest against the sides of the gear compartment |42. Pulling the trigger raises the yoke control rod |98 whose conical head |91 (see Fig. 15) wedges the two yoke arms moves them away from the wire 50. Thus, pulling the trigger stops the feeding of wire to the nozzles and stops the spraying of metal. When the trigger is released and the drive Wheels engage a wire or rod between them, they automatically grip the wire or rod tightly, because the drive gears |15, |16 act on the drive wheel pinions |82, |83 and push them and the yoke arms toward each other.

The wire guide 220 (see Fig. 1l) screws into a boss 22| on the top of the top gear case cover. The bore 222 of this wire guide is aligned with the bore 66 of the gas nozzle 56 and its rear end 223 is flared so as to facilitate the insertion of the wire therein. The forward end of the wire guide 222 is spaced from the rear end of the extension 65 on the gas nozzle 56, the space between the two lying between the drive wheels so that the drive wheels pressed together by 'the spring 2|0 can engage the wire 50.

In the forward part of the base 8 (see Fig. 1)

there is a transverse horizontal hole 224 by means of which the spray gun can be mounted on a support when it is not desired to hold it in the hand. This facilitates mounting the gun on the tool carriage of a lathe to deposit a uniform layer of metal on an article being rotated in the lathe and in mounting it on an extension handle or other support.

Although they have not been shown in the the drawings, in order to avoid complication. the gun is provided with suitable gaskets under all the various cover plates and between the various parts of the gun which are bolted or screwed together so that all the compartments, ducts, and chambers in the gun are proof against the leakage of oil, grease, air or gas, whichever they may contain.

A metal spray gun of thepr'esent invention is is very desirable from the standpoint of operation in that it provides a compact and easily handled device which is readily operated by the operator and which requires the minimum of attention from the operator during the metal spraying operation.

The flame in the flame nozzle is controlled by a manually operable valve |1 which acts as a mixing chamber or valve for the fluid fuel which is supplied to the llame nozzle, this fluid ordinarily being a mixture of oxygen and acetylene, the proportions and amounts of which are regulated by the pressure-reducing valves (not shown) on the supply tanks or cylinders commonly used for storing such fluids. After the proper mix'- ture is obtained, the operator turns the valve |1 to the "on position and the mixture of oxygen and acetylene passes through ducts in the body portion of the gun to the gas nozzle 56. After passing through the gas nozzle 56, the fuel is ignited in the flame nozzle 53 and the heat resulting therefrom is brought to bear upon a metal, such for example as the feed Wire 50, causing it to become melted as it passes continuously into the llame. The metal becomes melted in the flame nozzle bore 68 and is there atomized by the atomizing air passing through the atomizing air jets 12. Air is supplied to the atomizing air jets from the atomizing air chamber 5|, to which air is supplied through the atomizing air duct '13. `The air passing through the atomizing airjets 12 forms a spray which thereafter carries the molten metal in finely com-- vminuted form to the article or object upon which the metal is to be deposited. The metal at this time is in the condition of a fluid mist or spray and becomes solidified almost immediately upon coming in Contact with the article orv object upon Vwhich it is to be deposited.

The metal is fed to the atomizing nozzle by means of feeding wheels |90 which are power driven by means of a positive displacement iiuid pressure motor mounted in the body of the spray gun and operatively connected with said feeding wheels by means of a speed reduction gearing mechanism. The drive wheels are mounted on pins |19 which are movable relative to the wire in such a manner that variations in sizes of the wire are accommodated by movement of the dive wheels relative to the longitudinal axis of the wire. The feeding wheels |90 may be moved outwardly away from the wire at the will of the operator, and so out of driving relation to the wire, by manipulation of the trigger 205 which moves a pin |98 carrying a conical head portion |91 in an upward direction and so causes an outward movement of the pins |19 and the attached feeding wheels |90 away from engagement with the wire. During the time of this movement, however, the drive wheels I9!)l are still in the positive driving relation with the fluid pressure motor but do not engage the wire which is to be fed therethrough.

The fluid pressure motor which is herein provided is of the positive displacement type and is provided with exhaust ports which communicate with a chamber in the interior of the hollow handle 'l wherein the sounds carried :by the exhaust are muffled. Thus the gun of the present invention is comparatively silent in operation, noises attendant upon the operation of a positive displacement fluid pressure motor being largely attenuated in the muflling chamber inside the handle 1.

I claim: 1

i. A metal spray gun comprising means for melting, atomizing and spraying a metal, and a metal feeding device adapted to feed metal to said means for melting, atomizing and spraying metal and actuated by a motor, said feeding device comprising opposed movable feeding rolls located on `opposite sides of the path of the metal to be fed through the gun, said rolls being resiliently mounted and maintained in a position to yieldingly grip the metal passing therethrough ,and to move synchronously n'response to variations in sizes of the metal to be fed therethrough. 2. A metal spray gun comprising a spray head having metal melting and fluid pressure atomizing jet holes therein, a metal feeding passage in said spray head, a metal feeding device for feeding metal through said passage, and a control interposed between said passage and said feeding device and adapted to keep the melting flame forward of said passage, said control comprising means forming a passageway leading to said metal feeding passage and means for directing fluid under pressure to said passageway.

3. A metal spray gun comprising 'a spray head having metal melting and fluid pressure atomizing iet holes therein, a metal feeding passage in said spray head, a metal feeding device for feeding metal through said passage, and a control interposed between said passage and said feeding device and adapted to keep the melting flame forward of said passage, said control comprising a iet discharging at a point between said passage and said feeding device, and a port communicat-v ing with said jet to supply a flow of fluid under pressure which is discharged as a iiuid curtain between said passage and said metal feeding device.

4. A metal spray gun having a spray head, fuel jet holes in said spray head, a fuel supply system communicating with said jet holes, a valve forming a part of said system and comprising a movable valve member having a chamber therein for admixing fiuids to provide the fuel supplied to said jet holes, and ports extending through said member and communicating with said chamber to supply unrnXed fuel forming fiuids thereto.

5. A metal spray gun comprising a spray head, a ame nozzle therein, atomizing jets associated with said head, a fuel supply system forfurnishing a fluid fuel to said fiame nozzle and a fluid supply system for furnishing a uid to said atomizing jets at pressures different from the fluid pressures on the fuel supplied to said flame nozzle, a control valve associated with said systems and adapted to control by a single operation the flow of fuel t'o said nozzle and of fluid under pressure to said atomizing jets,and a duct discharging to the atmosphere concentric with said valve and interposed between ports communicating with said fuel supply system and ports communicating with said atomizing fluid supply system whereby fuel or atomizing fluid seepage around said valve is entrapped and carried away from said valve without affecting the relative differences in pressures between said fuel and said atomizing` fluid. l

6. A metal spray gun of the class described comprising a body,"fa burner, a movably mounted feed roller adapted to feed a wire to said burner, means to drive said feed roller comprising a power actuated shaft having its axis eccentric with the axis of said feed roller and means adapted to transmitpower from said shaft to said feed roller, the shaft being so located that the driving force transmitted to said feed roller presses said feed roller towards the wire.

7. A metal spray gun of the class described comprising a body, a handle, a burner, a movably mounted feed roller adapted to feed a wire to said burner, means to drive said feed roller, a trigger forward of said handle adapted to `inove said feed roller in relation to said wire.

8. In a metal spray gun adapted to melt unmelted material and to atomize and spray the molten material, a substantially cylindrical gas nozzle associated therewith and having a channel in the outside cylindrical surface and between` the ends of said nozzle, and material melting fuel jet holes in said nozzle communicating with said channel.

9. A metal spray gun comprising means for melting a metal wire, and for atomizing and spraying the molten metal, and a wire feeding. device adapted to feed wire to said means for melting, atomizing and spraying, said feeding device comprising feeding rolls adapted to rotate on movably mounted non-rotating pins, means for driving said feed rolls, and means for moving said pins in reference to said wire,

l WILLIAM M. BRITTON. 

